A side channel pump or compressor of the type to which this invention is directed is disclosed in Germany published Application No. 1-921945. As is explained in the introduction to the latter application, side channel compressors with axial flow are heretofore preferred because the flow characteristics thereof could be calculated more easily. Flow characteristics of side channel compressors with radial blades cannot be calculated according to prevailing opinion so that one is forced to use empirical data for the determination of the connection between the volume through-put and pressure because of the complexed flow.